使用observe_internet_connectivity包。

可用的特性

检查设备是否有互联网连接

  final hasInternet = await InternetConnectivity().hasInternetConnection;
  if (hasInternet) {
    //You are connected to the internet
  } else {
    //"No internet connection
  }

通过流收听互联网连接变化

  final subscription =
      InternetConnectivity().observeInternetConnection.listen((bool hasInternetAccess) {
        if(!hasInternetAccess){
          showToast('No Internet Connection');
        }
      });

   await Future.delayed(const Duration(seconds: 10 ));
   subscription.cancel();

使用InternetConnectivityListener监听flutter小部件内的互联网连接变化

    return InternetConnectivityListener(
      connectivityListener: (BuildContext context, bool hasInternetAccess) {
        if (hasInternetAccess) {
          context.showBanner('You are back Online!', color: Colors.green);
        } else {
          context.showBanner('No internet connection', color: Colors.red);
        }
      },
      child: Scaffold(
        body: Container(),
      ),
    );

使用InternetConnectivityBuilder构建互联网连接感知小部件

    return InternetConnectivityBuilder(
      connectivityBuilder: (BuildContext context, bool hasInternetAccess, Widget? child) { 
        if(hasInternetAccess) {
          return OnlineWidget();
        } else {
          return OfflineWidget();
        }
      },
      child: ChildWidget(),
    );

使用

dependencies:
  connectivity: ^0.4.2

我们从资源处得到的是

      import 'package:connectivity/connectivity.dart';

      Future<bool> check() async {
        var connectivityResult = await (Connectivity().checkConnectivity());
        if (connectivityResult == ConnectivityResult.mobile) {
          return true;
        } else if (connectivityResult == ConnectivityResult.wifi) {
          return true;
        }
        return false;
      }

未来对我来说没什么问题，我们必须每次都实现它，比如:

check().then((intenet) {
      if (intenet != null && intenet) {
        // Internet Present Case
      }
      // No-Internet Case
    });

所以为了解决这个问题，我创建了一个类，它接受一个布尔isNetworkPresent参数的函数，就像这样

methodName(bool isNetworkPresent){}

实用工具类是

import 'package:connectivity/connectivity.dart'; class NetworkCheck { Future<bool> check() async { var connectivityResult = await (Connectivity().checkConnectivity()); if (connectivityResult == ConnectivityResult.mobile) { return true; } else if (connectivityResult == ConnectivityResult.wifi) { return true; } return false; } dynamic checkInternet(Function func) { check().then((intenet) { if (intenet != null && intenet) { func(true); } else{ func(false); } }); } }

并使用连接检查实用程序

  fetchPrefrence(bool isNetworkPresent) {
    if(isNetworkPresent){

    }else{

    }
  }

我将使用这种语法

NetworkCheck networkCheck = new NetworkCheck();
networkCheck.checkInternet(fetchPrefrence)

我已经创建了一个包，(我认为)可以可靠地处理这个问题。

在pub.dev上的包

这个包在GitHub上

欢迎讨论。你可以使用GitHub上的问题跟踪器。

---

我不再认为这是一个可靠的方法:

---

想在@Oren的回答中添加一些东西:你真的应该再添加一个catch，它将捕获所有其他异常(为了安全起见)，或者只是完全删除异常类型并使用一个catch，它处理所有异常:

案例1:

try {
  await Firestore.instance
    .runTransaction((Transaction tx) {})
    .timeout(Duration(seconds: 5));
  hasConnection = true;
} on PlatformException catch(_) { // May be thrown on Airplane mode
  hasConnection = false;
} on TimeoutException catch(_) {
  hasConnection = false;
} catch (_) {
  hasConnection = false;
}

或者更简单…

案例2:

try {
  await Firestore.instance
    .runTransaction((Transaction tx) {})
    .timeout(Duration(seconds: 5));
  hasConnection = true;
} catch (_) {
  hasConnection = false;
}

基于这个答案https://stackoverflow.com/a/68436867/10761151

如果你使用dart零安全，你会得到一个错误， 因此，您可以将依赖项data_connection_checker: ^0.3.4更新为internet_connection_checker: ^0.0.1+2

你可以用这个代码

import 'dart:async';
import 'package:connectivity_plus/connectivity_plus.dart';
import 'package:internet_connection_checker/internet_connection_checker.dart';

class ConnectionUtil {
  static final ConnectionUtil _singleton = new ConnectionUtil._internal();
  ConnectionUtil._internal();

  static ConnectionUtil getInstance() => _singleton;

  bool hasConnection = false;

  StreamController connectionChangeController = StreamController();

  final Connectivity _connectivity = Connectivity();
  void initialize() {
    _connectivity.onConnectivityChanged.listen(_connectionChange);
  }

  void _connectionChange(ConnectivityResult result) {
    _hasInternetInternetConnection();
  }

  Stream get connectionChange => connectionChangeController.stream;
  Future<bool> _hasInternetInternetConnection() async {
    bool previousConnection = hasConnection;
    var connectivityResult = await (Connectivity().checkConnectivity());
    if (connectivityResult == ConnectivityResult.mobile || connectivityResult == ConnectivityResult.wifi) {
      // this is the different
      if (await InternetConnectionChecker().hasConnection) {
        hasConnection = true;
      } else {
        hasConnection = false;
      }
    } else {
      hasConnection = false;
    }

    if (previousConnection != hasConnection) {
      connectionChangeController.add(hasConnection);
    }
    return hasConnection;
  }
}

在有状态小部件上可以实现此代码

  bool hasInterNetConnection = false;

  @override
  initState() {
    ConnectionUtil connectionStatus = ConnectionUtil.getInstance();
    connectionStatus.initialize();
    connectionStatus.connectionChange.listen(connectionChanged);

    super.initState();
  }

  void connectionChanged(dynamic hasConnection) {
    setState(() {
      hasInterNetConnection = hasConnection;
    });
  }

我写了一个包来检查活跃的互联网连接和显示相应的小部件。

flutter_no_internet_widget

例子:

InternetWidget(
 online: Text('Online'),
 offline: Text('Offline),
);

根据网络状态，将显示适当的小部件。如果您有一个活跃的互联网连接，一个在线小部件将显示。

所有重量级的工作都由包完成，您所要做的就是提供在线和离线小部件。您还可以提供一个加载小部件和查找URL。

欢迎讨论、提交意见书或提出建议。

这是我的解决方案，它检查互联网连接以及数据连接，我希望你喜欢它。

First of all add dependencies in your pubsec.yaml

dependencies:        
    data_connection_checker:

And Here Is The main.dart Of My Solution

import 'dart:async';

import 'package:data_connection_checker/data_connection_checker.dart';
import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: "Data Connection Checker",
      home: HomePage(),
    );
  }
}

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  StreamSubscription<DataConnectionStatus> listener;

  var Internetstatus = "Unknown";

  @override
  void initState() {
    // TODO: implement initState
    super.initState();
//    _updateConnectionStatus();
      CheckInternet();
  }

  @override
  void dispose() {
    // TODO: implement dispose
    listener.cancel();
    super.dispose();
  }

  CheckInternet() async {
    // Simple check to see if we have internet
    print("The statement 'this machine is connected to the Internet' is: ");
    print(await DataConnectionChecker().hasConnection);
    // returns a bool

    // We can also get an enum instead of a bool
    print("Current status: ${await DataConnectionChecker().connectionStatus}");
    // prints either DataConnectionStatus.connected
    // or DataConnectionStatus.disconnected

    // This returns the last results from the last call
    // to either hasConnection or connectionStatus
    print("Last results: ${DataConnectionChecker().lastTryResults}");

    // actively listen for status updates
    listener = DataConnectionChecker().onStatusChange.listen((status) {
      switch (status) {
        case DataConnectionStatus.connected:
          Internetstatus="Connectd TO THe Internet";
          print('Data connection is available.');
          setState(() {

          });
          break;
        case DataConnectionStatus.disconnected:
          Internetstatus="No Data Connection";
          print('You are disconnected from the internet.');
          setState(() {

          });
          break;
      }
    });

    // close listener after 30 seconds, so the program doesn't run forever
//    await Future.delayed(Duration(seconds: 30));
//    await listener.cancel();
    return await await DataConnectionChecker().connectionStatus;
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Data Connection Checker"),
      ),
      body: Container(
        child: Center(
          child: Text("$Internetstatus"),
        ),
      ),
    );
  }
}